What should the pressure be on a Baxi?
The pressure on a Baxi boiler should be between 1 and 2 bar. That is the range Baxi gives in its homeowner advice and its current installation manuals, and it applies across the 400, 600 and 800 series, combi and system. On a dial gauge, the needle should sit in the green section.
When the boiler is heating, Baxi says the needle will go up a little but should not go higher than about 2.5 bar. If it falls below 1 bar, Baxi says you need to repressurise it, and that most people can do this themselves without calling an engineer.
Baxi's range is a little wider than some brands, which tend to quote 1 to 1.5 bar. For a side by side comparison, and what the reading means with the heating on and off, see our guide to normal boiler pressure.
Which Baxi do you have?
Baxi's 400, 600 and 800 boilers come in two generations, and they show pressure and fault codes differently. Look at the name on the front or on the data badge under the boiler:
- The original 600 and 800 Combi and System have a round pressure gauge on the front, and many have a green Easy-Fill filling link underneath. They use E-codes, such as E118 for low pressure.
- The Combi 2 and System 2 ranges (such as the 200, 400, 600 and 800 Combi 2 and the 600 and 800 System 2) have a digital pressure reading on the front and use codes in the format A.02.06.
If there is a 2 after the word Combi or System on the front, you have the newer generation.
Baxi also sells boilers outside these series, such as the Assure, Platinum and MainEco ranges. The same 1 to 2 bar guidance applies, and Baxi's error list shows several of them share the E118 low pressure code with the original 600 and 800.
Baxi pressure by generation
| Range | How pressure is shown | Normal reading | Low pressure code | Filling method |
|---|---|---|---|---|
| Original 600 and 800 Combi and System | Round dial gauge on the front | 1 to 2 bar, needle in the green | E118, water pressure low (below 0.5 bar) | Green Easy-Fill link under the gauge on many models, or an external loop |
| 200, 400, 600 and 800 Combi 2 | Digital reading on the front | 1 to 2 bar; top up below 0.8 bar | A.02.06, then H.02.07 if it stays low | Easy-Fill link underneath; the 800 Combi 2 has a permanent filling link |
| 600 and 800 System 2 | Digital reading on the front | 1 to 2 bar | A.02.06, then H.02.07 | Filling loop fitted by the installer on the system pipework |
Codes are from Baxi's published error code list, and the 0.8 bar top-up point and permanent filling link are from the Baxi 800 Combi 2 installation and service manual. If your model is not listed, the user guide for your boiler, on the Baxi website, takes priority.
Baxi low pressure codes
A Baxi boiler with low pressure usually tells you with a code before you notice the gauge. Which code you see depends on the generation:
- E118 on the original 600 and 800 ranges, the Assure, Platinum and several older compact models. Baxi's error list describes it as water pressure low, below 0.5 bar.
- E119 on many older Baxi boilers, where the water pressure switch has not made because there is not enough pressure.
- A.02.06 on the Combi 2 and System 2 ranges, meaning low system pressure in the heating circuit.
- H.02.07 on the same ranges, meaning the pressure in the heating circuit is permanently low. The boiler has stopped and needs topping up.
Once the pressure is back in range, the code may clear on its own or you may need to reset the boiler. Our guide to resetting a Baxi boiler shows where the reset control is.
Where is the filling loop on a Baxi?
On most Baxi combi boilers the filling link is underneath the boiler. Baxi's guidance for boilers with a round gauge on the front says there is a green Easy-Fill filling link underneath, and its guidance for the latest digital models also points to a green Easyfill link under the boiler. The 800 Combi 2 installation manual describes a permanent filling link supplied with the boiler, designed so that nothing has to be removed after filling.
On a system boiler, which has no cold mains connection of its own, the installer fits a filling loop on the pipework. It is usually a braided hose with two valves, under the boiler or near the hot water cylinder. Our filling loop guide explains how this type works and why it must be disconnected after use.
How do I repressurise a Baxi boiler?
To repressurise a Baxi boiler, operate the filling link slowly while watching the pressure, and stop once it reads between 1 and 2 bar. Baxi publishes short videos for both gauge types and asks you to watch them to the end before you start. The general steps are:
- Let the system cool. Turn the heating off and wait for the radiators to cool, so the reading is a true cold pressure.
- Find the filling link. Look under the boiler for the green Easy-Fill lever, or the braided hose and valves on a system boiler.
- Open it slowly. Operate the green lever gently, or open the loop valves one at a time. You will hear water flowing.
- Watch the gauge or display. Keep watching as the pressure rises. Aim for about 1.5 bar, the middle of Baxi's range.
- Close it fully. Return the lever to its closed position, or close both valves and disconnect the hose.
- Check the reading again after a few minutes, and reset the boiler if a code is still showing.
On the Combi 2 ranges the digital reading makes it easy to stop at the right point. The 800 Combi 2 manual says to top up once the pressure is lower than 0.8 bar, bringing it back to between 1 and 2 bar.
Aim for the middle of the range rather than the top. Filling to 1.5 bar leaves room for the rise when the heating runs, so the pressure stays well below the 2.5 bar Baxi gives as the upper limit.
Baxi boiler pressure too high
If a Baxi reads well above 2 bar when cold, or above about 2.5 bar when hot, it is too high. Baxi says a safety valve is fitted that will discharge water to keep the pressure at a safe level, and on the 800 Combi 2 that valve is set at 3 bar. Baxi's advice is that you may need to bleed a radiator to bring the pressure down. On older models a high pressure fault shows as E117.
If you have just topped up, check that the green lever has returned fully to closed. If the pressure is normal cold but climbs each time the heating runs, the expansion vessel is the likely cause, and our guide to boiler pressure that is too high explains the next steps.
When to call a Gas Safe registered engineer
Baxi says that if you need to keep topping up the pressure, it could indicate a problem, and you should contact your Gas Safe registered installer or Baxi Customer Support. Call one if:
- The pressure falls below 1 bar again within days or weeks.
- A low pressure code returns after the gauge showed 1 to 2 bar.
- The pressure rises above 2.5 bar with the heating on, or water drips from the pipe outside.
- The Easy-Fill lever does not raise the pressure, or lets water in when closed.
Only use the filling link underneath the boiler. Never remove the boiler casing to look for a leak or reach the pressure switch; those parts sit next to gas and electrical connections and are for a Gas Safe registered engineer only.
While you wait, our guide to a boiler losing pressure lists the checks you can make yourself at radiators, valves and the relief pipe outside, so you can tell the engineer what you found.